Edward  victor esfcnhahn



- soluble compounds.

PATENT OFFICE.

EDWARD VICTOR ESPENHAKN, 01' EAST ORANGE, NEW JERSEY.

PROCESS FOR BECOVEBING CYAINOGEN COMPOUNDS.

Specification of Reissued Letters r ate nt. Reissued A 19 1,921 I Io lhawing. Original 110. 1,315,219, dated September 9, 1919, Serial No. 178,943, filed July 6, 1917.

Application for reissue filed January 17, 1921. Serial No. 438,046.

To all whom. it my camera Be it known that I, EDWARD VIo'roR Esramumv, a subject of the King ofGreat Britain, and a resident of East Orange,

ments in the treatment of gases obtained from coal and other carbonaceous fuel and refers more es cially to the treatment of heating and il uminating gases containing c anogen bearing compounds obtained from I e distillation of coal in ordinary gas w rks or from the manufacture of coke in co e ovens.

This invention is also applicable toiother gases which contain cyanogen bearing compounds (such as producer gas and blast furnace gases). I

The object of this invention is to provide means for the recoveryof cyanogen hearing compounds from such gases and also other by-products such as sulfate of ammonia. A further object of this invention is to rovide amethod of treatment which is cyc ic in operation whereby the products of subsequent operations are reusable 1n the treatment of fresh supplies ofcrude gases.

Hitherto many attempts have been made to extract soluble ferro-cyanids from coal and coke oven gases but up to the present these attempts have been more or less unsuccessful owing to theformation of in- These failures have been experienced both when the ammonia has been previously removed and when ammonia is present. In cases where ammonia has not been removed its presence, by slightly increasing the alkalinity, at first assists the absorption of the cyanogen-bearing substances, but after a certain point has been reached insoluble ferro-cyanids have been formed.

I have discovered that. if the absorption of the cyanogen bearing substancesis carried out at relatively high temperatures (say from 40 to 90 C. approximately the dew point) or at the temperatureordinarily employed for direct recovery and 1f the solution is maintained at a relatively high state of concentration approximately the point of- 06 saturation the formation of insoluble ferrocyanids is avoided irrespective of the presonce of ammonia even if present in comparatively large proportions.

I accomplish the objectsof this invention by providing a method of treatment which comprises submitting the gases at a relatively high temperature to treatment with aconcentrated alkaline solution (such as sodium carbonate) containing sodium ferrousferro-cyanid in suspension until the solution becomes charged with sodium ferrocyanids; then allowing the solution to cool for the crystallization of the sodium ferrocyanld, then treating the sodium ferrocyanid thus obtained with an acid '(such as sulfuric acid) for the formation of hydrocynnic acic (and subsequently alkaline cyanids) and sodium ferrous-ferro-cyanid which latter may be advantageously used with sodium, carbonate for treatingthe crude gasesin the first operation. The gases after the removal of the cyanogen bearing compounds and containing ammonia and sulfureted hydrogen may be passed through a solution of ferrous sulfate for the formation of ferrous sulfid for use in producing the sodium ferrous-ferro-cyanid.

This invention is applicable to the treatmcnt of gases either by the direct? or the semi-direct methods for the recovery of ammonia and may be applied either before or after the removal of the ammonia.

By way of ex..mple I will describe the treatment according to this invention of ordinary coke oven gases obtained from the destructive distillation of coal in which the recm'ery otthe cyanogen bearing compounds is effected before the removal of the ammonia. 'lhe gases are first treated in the ordinary. centrifugal or other washers for the removal of tar fog and without cooling i are led into washers preferably of the centrifugal type at a temperature of approximately the dew point of the gases (i. e.

from 40 C. to 90 C.) and while still at that temperature are brought into intimate contact with a washing'liquor, which consists of a concentrated solution of sodium carbonate in which sodium ferrous-ferro cyanid is held in suspension.

The produc- 1 a so 'f solviligffourflbs. of dehydrated soc iumcar bonate fper fgallon-of' water well answers is in accordance 'with' the following equa-.

culation.

furic acid to form sodium ferrous-ferro' cyanid. The extent of concentration of this solution of sodium carbonate is obtained by adding" the re uisite quantity of such -reagent as calcu ated to obtain subsequently ar -concentrated solution'of sodium carbonandj ferro-cyanid. I have found rictiuethat a solution made u by disthe purpose.) In praetice' preferably two or more separate tanks or containers of this l quor are-maintained; so that as through the said; liquor-while the same is Qmaintainedin a constant state o f agitation the centrifugal action of the washer.

b. Allie temperature is umintained at or about thedew' point of the gases by the admission v ofsteam or other heating medium as may be found necessary, In raetice sodium ferrous-ferro-cyanid may added from timetotime to maintain the reaction which tank has become sufficiently charged with sodium ferro-cyanid the liquor contained in the second tank is by-passed into the first as washer and the first mentioned liquor is withdrawn and the sludge separated from the clear li uor such as by'filter pressing or the like. e clear liquor is then allowed to cool when pure crystals of sodium ferrocyanid are formed. The clear liquor is r turned to the washing storage tank after having been renewed b the addition of sodium carbonate and so ium ferrous-ferrocyanid. The sodium-fen -c anid obtained as above is treated with ls'ul furic acid \for the formation of hydrocyarlic acid (and subsequently alkaline cyanide) in; accordance with the followlng equatiofh The hydrocyanic acid thu formed is used for producing alkaline cyanide in'known manner. The sodium-ferrous-ferro cyanid gases. The ferrous s\1lfid foi-med as above Wreacts with sodium carbonate-and with the FeS +2 UN compounds inthe gases for the formauni ferro-cyanid, according to the equation:-

The gases after the removal of the cyanogencyanogen bearing compounds and ferrous sulfid 1n accordance'with the following equation I W g: The ferroussulfidaobtained as above may be' one is infi withdrawn the other is in eir- 4 he. gases arecaused to pass used in eoiqunction. with sodium carbonate afor washing-the crude gases as above describedfor vthe iormation of sodium ferroeyanid, l a

Anotherfixample of this invention con sists of its-application to the treatment of gases in which the cyanogen bearing com pounds are recovered after the removal'of the ammonia. In this case the gases are treated in the ordinary way for the removal of the tar fog and anm'ionia and are then subjected to a washing treatment at a rela tively high temperature (approximately the dew point of the gases) with a concentrated solution of sodium carbonate in which so 'dium ferrous-ferro-cyanid is held in suspension. The same reactions take place as described above producing sodium ferro cyanid in solution. The liquors are treated. for the separation of the' slud e and the clear solution is allowed to'cool %or the precipitation of crystals of pure sodium ferrocyanid. This sodium ferro-cyanid is'trcated with sulfuric acidffor the formation of hydrocyanie acid and subsequently alkaline cyanide while the sodium ferrous ferrocyanid formed is used with the concentrated ,solution of sodium carbonate for treating 'fresh supplies of thegases for, the formaits tion of sodiumierro-cyanid as previously described. v y

A certain portion ofthe gasesb'efore being ledinto the ammonia saturators is byspassed into another washer where the said gases 4 1 1 n containingammonia and 'sulfureted hydrolCN+3Na,SO;.

gen are caused to pass through a solution of ferrous sulfate for the formation of ammonium sulfate andferrous sulfid." This ferrous sulfid may be used as above described for'treat-in'g fresh gases .with a concentrated ,solutiorio'f sodium carbonate for the formation of sodium ferro-cyanid.

, 'Iclaimi 1. In the treatment gases obtained by the heat-treatment of coal and, other can bonaceous-fuel, submitting the said gases at a relatively high temperature corresponding approximately to the dew point of the said gases: to a treatment with aconcentratedsolution of an alkali containing sodium ferrous ferro-cyanid in suspension.

2. The method of treating gases obtained by the heat-treatment of coal and other carbonaceous fuel, which comprises separating the tar fog; then submitting the said gases to a washing operation at a relatively high tem erature corresponding approximately to te dew oint of'the said gases, with a concentrated solution of sodium carbonate containing sodium ferrous ferro-cyanid in suspension until the solution becomes charged with sodium ferro-cyanid, allow ing the solution to cool until the sodium ferro-cranial crystallizes out; treating the said sodium ferro-cyanid with acid for the formation of hydrocyanic acid and sodium ferrous ferro-c anld; and washing afurther amount 0 the said gases with a concentrated solution of sodium carbonate containing this sodium ferrous-ferro-cyanid.

3. Method of treating gases obtained from coal and other carbonaceous fuel consisting of first treating the saidgases for the removal of the tar fog; treating such gases for the absorption of ammonia: submitting the gases to treatment with a concentrated solution of sodium carbonate containing sodium ferrousferro-cyanid in suspension until the solution becomes charged with sodium ferro-cyanid; allowing the said solution to cool until the sodium ferro-cyanid crystallizes out; treating the said sodium ferro-cyanid with acid for the formation of hydrocyanic acid and sodium ferrous ferrocyanid; and utilizing such sodium ferrous ferro-cyanid for treating fresh gases in conjunction with a concentrated solution of sodium carbonate.

4. In the treatment of coal gas, coke oven gas and the like, the process of recovering cyanogen compounds contained therein, which comprises passing such gas, while warm, into contact with a concentrated solution of an alkali containing an ir n compound capuhle of uniting with the said cyanogen compounds.

5. in the treatment of coal gas, coke oven gas and the like, the process of recovering cyanogen compounds contained therein, which comprises passing such gas, while warm, iiito'contact with a concentrated solution of an alkali containing an iron compound capable of. uniting with the said cyanogen compounds, and thereafter removing a cyanogen-alkali-iron compound from the liquor and regenerating therefrom an iron compound suitable for use in the first art of the process;

6. The step of treating cyanogenrontaining gas with a concentrated solution of soda containing in suspension an iron compound capable ofreacting with the .soda and the 05 dew point.

7'. Ill tile treatment of gases produced in the heat-treatment of coal, which gases contain cyanogen, the step of washing such gases with a liquor comprising sodium ferrous ferro-cyanid, suspended. in a concentrated soda solution, while at about the dew point of the gases.

8.. .n a process for recovering cyanogen compounds, the steps which comprise form ing a solution of sodium ferro cyanid, crystallizing the sodium ferro cyanid therefrom, treating the crystallized sodium ferro cyanid to form hydrocyanic acid and sodium ferrousferro cyanid, and utilizing the sodium ferrous ferro cyanid for the formation of 'additional sodium ferro cyanid solution.

9. In a process for recovering cyanogen.

the insoluble cyanogen compound for the formation of additional solution of the complex compound. of cyanogen and a heavy metal.

10. In a process for recovering cyanogen .co|npounds,the steps which comprise forming a solution of complex cyanogen compound, crystallizing such complex cyanogen compound from the solution, treating the same with acid to generate hydrocyanic acid and an insoluble complex cyanogen compound, and utilizing the insoluble complex cyanogen compound for the formation of an additional solution of the first mentioned complex cyanogen compound.

11. In a process for recovering cyanogen compounds. the steps Which comprise forming a solution of at complex cyanogen compound, crystallizing such complex compound from the solution, treating the same with acid to generate hydrocyanic acid and an insoluble complex cyanogen compound, and utilizing the insoluble cyanogen compound thus formed and the liquor from which the first complex cyanogen compound is crystallized, to form additional solution of first mentioned complex cyanogen compound.

12. In a' process for recovering cyanogen compounds, the steps which comprise forming a solution of sodium ferro cyanid, crystallizing the sodium ferro cyanid from the solution, treating such crystallized sodium ferro cyanid withacid to produce hydrocyanic acid and insoluble sodium ferrous ferro cyanid, and utilizing the insoluble sodium ferrous ferro cyanid and the liquor compounds, formin El'solutibn of sodium ferro cyanid, crysta lizing the sodium fen-o cyanid from the solution an'd treating the same with acid to produce hydrocyanicacid 5 and sodium ferrous ferro cyanid.

14. In a process for recovetin 'cyano a comp ex compounds, forming a solution 0? .mogcn compound, crystallizintf s'ucb comex cyanogen com und from 1e solution, treating the or sta lized complex cyan compound wit acid.- to nci'am hy cylinic acid and an insolu 1c complex cyanogen compound.

' EDWARD' VICTOR ISPIIIIAHI. 

